Metal Detector Coils - What Coils are Best For Gold Prospecting Ground Conditions

Metal detector coils need to match your metal detector and be suited to the type of ground you are prospecting to find gold.

There is no point in using a small coil in deep gold nugget areas - they just wont penetrate the depth that you want (Unless there is a huge gold nugget down there). Even if there is a huge nugget just below the coils reachable depth a small coil wont detect it!

How deep you find gold will depend on the size of the nugget, the size of the coil and your metal detector settings!

Mono Coils - Your Coil Of FIRST Choice

A Mono Coil can be more noisy than a DD coil but can be more sensitive but WILL provide more depth and sensitivity than a similar sized DD coil in finding gold nuggets.

Here is a video showing the use of a small Mono Coil and comparing the sounds of a Minelab 11' mono coil and a 8x6" Nuggetfinder Sadie Mono on both a Minelab 4500 and 5000;

There is 3 common types of coils that we are concerned with for gold nugget prospecting, Monoloop, Double D and Concentric.

Monoloop metal detector coils have one winding around the outside circumference of the coil and this wire is used to transmit and receive.

The search Pattern is cone shaped which means the search pattern narrows at depth.

You need to overlap your search pattern to prevent missing gold at a slightly greater depth than the edge of the cone.

This is one of the reasons why the proper techniques decribed in Chaining for Gold are critical to finding all the gold in the area you want to clean out.

The mono coils go deeper than the DD coils and with Minelab 5000 and 4500 detectors they have significant benefits over DD coils and should be your FIRST CHOICE of coil used.

Double D Metal Detector Coils

The Double D has two loops of wiring (like reversed D's that meet in the middle of the coil) which overlap in the middle of the coil. One coil used as a transmit and the other as the receive signal antenna.

Where the two coils overlap in the middle of the search coil is the main detection zone which is narrow but consistent at depth.

This means that the speed of sweep is very important, if the coil sweep is too fast it will not pick up or eliminate small targets or weak signals a the edge of detection.

Unlike the monoloop coil which has a cone shaped detection zone the size of the diameter of the coil wiring at the top. The detection zone decreases in size at depth.

DD coils are less sensitive to ground noise than Monoloop coils because the coil wirings are smaller than those on the perimeter of a Monoloop coil.

The smaller receive wirings un the coil means that less ground noise is detected and amplified so it is not as noisy.

The DD wired coil has a natural tendency to eliminate most of the ground signal, while at the same time it still responds with a strong signal from target objects.

Concentric Coils

Have two circles of wire winding, one inside and one outside.

These coils pinpoint and discriminate well because the strongest signal is in the centre of the coil.

They are used as metal detectors designed for treasure hunting such as jewellery and coin hunting because they can discriminate small metal objects well at a shallow depth.

Anti Interference or Salt Lake Metal Detecting Coils

AI Coils (or Salt coils) were originally designed to combat power interference from power lines but they are also minimise interference from heavy salt deposits.

This page explains more about the settings and benefits and tests the Coiltek AI Coils.

Chart Showing Metal detector Coil Differences and The Best Coil to Use

Condition Or Size of Gold Nuggets

Monoloop Coils

Double D Coils

Small Gold - less than 2 grams

More Sensitive to small gold in all coils

With the Minelab 4500 we are picking up small sub 1 gram bits with larger mono coils.

The Minelab 5000 on FIne Gold with a small Nuggetfinder Sadie 8x6 inch coil is deadly for small gold.

Small coils sensitive to small gold.

Larger coils not as sensitive to small gold.

Larger Gold Nuggets

The larger the coil the deeper the nugget that can be found

The larger the coil the deeper the nugget that can be found.

Will not penetrate as deep as a Monoloop of same size. But will remove ground noise,

Ground Coverage

Cone Shaped detection area - larger coverage at coil face which tapers off at depth

Essential you overlap detector sweeps or you will miss gold at depth.

Greater ground coverage per sweep.

Will not penetrate as deep as Mono coils.

Due to narrower detection zone speed of sweep whould be slower.

Sweeping too fast may miss small gold because the signal may be filtered out.

Noisy or Mineralised Ground

More sensitive to mineralisation,hot rocks and ironstone.

More difficult to tune than a DD coil

Can be noisier than and DD and dificult to ground balance - the larger the coil the more difficult.

Quieter than a Monoloop coil in mineralised ground.

Can be used in noisy ground where a monoloop may not function well

Discrimination Mode

Discrimination is the ability to distinguish different metal signals e.g. Ferrous and Gold.

Doesnt work in Mono coils

Will discriminate.

Not advisable to use discrimination when searching for gold nuggets - dig every target!

Motion and Coverage

Closer to the coil the detection coverage is right around the coil perimeter.

This means more coverage pushing the coil forward under shrubs and bushes than a DD.

Has a wedge shaped detecting profile which is better swung from side to side.

If you push it forward and back under vegetation you may miss some gold.

Shape and Size of Metal Detector Coils

The physical shape and size of coils will be based on the decision you need to make about the ground conditions where you prospect for gold.

There is two basic coil shapes, round and elliptical.

There is a huge variety of sizes in these configurations from 4 inches to 40 inches in size - depends what you want them for!

Small Coils - easy to use in thick scrub or rocky terrain, weigh less so they are easy to use.

Small Coils - More sensitive to small gold at shallow depth

Elliptical Coils - good search area and easier to use in thickly vegetated areas and spinifex covered ground.

Large Coils -Penetrate deeper to find gold nuggets and cover greater ground with each swing.

Large Coils - their disadvantage is that they are heavier and you could become fatigued quicker.

Large Coils - Can be noisier in mineralised ground and harder to tune - not as much an issue wiht the new Minelab 5000.

The larger the coil then the deeper it will penetrate generally but it will not be as sensitive to small gold.

The smaller coils will clean up the small gold at shallow depth and find larger pieces at a greater depth but not as deep as larger coils.

The small Nuggetfinder mono has exceptional sensitivity and good depth on the Minelab 5000 in "Fine Gold" Settings.

What Metal Detector Coil Is Best To Use?

Its your choice and it will depend on the type of ground you are prospecting and the size and depth of the nuggets you are targetting.

Work out the terrain and type of gold you will be hunting then at least purchase the additional metal detecting coils you need to better target your gold prospecting profile. You really need a small mono coil, medium and Large Coil to clean out a patch.